.transparent-black {
  /* Required for IE 5, 6, 7 */
  /* ...or something to trigger hasLayout, like zoom: 1; */
  width: 100%; 
  height:100%;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;

  background-color: #000000;  
  /* Theoretically for IE 8 & 9 (more valid) */ 
  /* ...but not required as filter works too */
  /* should come BEFORE filter */
  -ms-filter:"progid:DXImageTransform.Microsoft.Alpha(Opacity=50)";
  
  /* This works in IE 8 & 9 too */
  /* ... but also 5, 6, 7 */
  filter: alpha(opacity=90);
  
  /* Older than Firefox 0.9 */
  -moz-opacity:0.9;
  
  /* Safari 1.x (pre WebKit!) */
  -khtml-opacity: 0.9;
    
  /* Modern!
  /* Firefox 0.9+, Safari 2?, Chrome any?
  /* Opera 9+, IE 9+ */
  opacity: 0.9;
}